Just sharing a sample code to close quote as won through C#
WinQuoteRequest winQuoteRequest = new WinQuoteRequest();
Entity quoteClose = new Entity("quoteclose");
quoteClose.Attributes["quoteid"] = new EntityReference("quote", new Guid("015816C2-2F10-E611-8112-3863BB353ED0"));
quoteClose.Attributes["subject"] = "Quote Close" + DateTime.Now.ToString();
winQuoteRequest.QuoteClose = quoteClose;
winQuoteRequest.Status = new OptionSetValue(-1);
organizationProxy.Execute(winQuoteRequest);
Hope it helps..
